Forward Tracking Report of the Vienna iLCsoft Group Winfried A. Mitaroff “Discussion document”...

Forward TrackingReport of the Vienna iLCsoft Group

Winfried A. Mitaroff“Discussion document” at the

5th ILD Workshop and SiLC Meeting

LAL Orsay / APC Paris VII, May 2011

Vienna’s commitment to ILD

• MarlinReco’s Track Search and Reconstruction based on wrapped legacy Fortran 77 code (from LEP era).

• Urgent need to re-write this from scratch in C++.• HEPHY agreed in fall 2009, as a “significant contribution

to ILD”, to provide the new processor for tracking in the forward region (stand-alone track search shared).

• Required for processing data for the “Detailed Baseline Design” (DBD), i.e. to be released by spring 2012 !

• Scheduled start in October 2010 delayed until May 2011, due to problems recruiting a diploma/PhD student.

• Started with a new student (Robin Glattauer) on 9 May.

2Mitaroff: Discussion document at ILD#5 and SiLC22 - 26 May 2011

Forward region (ILD_00 layout)

Mitaroff: Discussion document at ILD#5 and SiLC22 - 26 May 2011

ϑ = 900

36.70

25.50

16.50

11.50

80

50

10 padrows →

FTD 1 2 3 4 5 6 7

Very forward region:– 5.00 < ϑ < 11.50: only FTD measuremts. contributing,– Range of FTD 1 (2) starts where that FTD 6 (7) ends.Intermediate region:– 11.50 < ϑ < 25.50: complex mix of VTX + FTD + TPC,– FTD: only FTD 1 … 3, plus FTD 4 until ϑ < 16.50,– TPC: 10 pad-rows @ 11.50 … 100 pad-rows @ 25.50.Barrel + FTD 1 only:– 25.50 < ϑ < 36.70: VTX + FTD 1 + SIT + TPC.ETD: ignored by track fitting (no more precision)– 9.80 < ϑ < 36.90: PR link to fwd. ECAL, useful in PFA.

Pixel disks Double-sided (stereo angle) strip disks

3

Forward tracking sub-tasks

1. FTD geometry description (done), \2. FTD drivers in Mokka (done), } not by Vienna

3. FTD digitizations in Marlin (missing). /4. FTD stand-alone track search –– shared task

(very fwd. and intermediate regions, 50 < ϑ < 25.50);Valencia’s stand-alone silicon track search may be evaluated for FTD.

5. TPC-supported track search(optional in intermediate region, 11.50 < ϑ < 25.50).

6. DAF-based final hit associations.

7. Precision forward track fit.

8. Region 25.50 < ϑ < 36.70 is “mostly barrel”(VTX, SIT, TPC) with only one FTD 1 barrel or fwd. task ?➯

22 - 26 May 2011 Mitaroff: Discussion document at ILD#5 and SiLC 4

Fwd. track search strategies• Stand-alone in FTD:

– This is the only possible strategy in the very forward region,

– Various algorithms exist – which to chose needs careful study,

– For small ϑ, hits from beamstrahlung-induced background may cause further problems (we need a reliable estimate),

– Layout for optimized track resolution (e.g. strip orientation and stereo angle) not necessarily optimal for track search.

• Combined TPC–FTD:– This may be an optional strategy for the intermediate region:

– Inward extrapolation of tracks found by local PR in the TPC,FTD hits tested against and associated to them,

– Timing problems hopefully solved by “time stamps”.

• Soft hit association:– Hits may be shared among tracks, and the final association relegated

to track reconstruction based on the DAF.


Forward track reconstruction

• Algorithms used:– Based on the Kalman Filter, with robustification by the adaptive

Deterministic Annealing Filter (DAF):– (1) Testing and updating the track hypothesis (hit associations)

by identifying and removing “outliers”, and resolving ambiguous associations from the track search,

– (2) Performing a precision track fit.

• Special features:– Flexible track navigation in the complex intermediate region,

coping with inclined or staggered plaquettes of FTD.– Energy loss of electrons modeled by the Gaussian Sum Filter

(GSF) requires ➯ extension of the LCIO data model,– Magnetic field distortions by the “anti-DiD” taken into account

(small “Billoir corrections” on helices, or Runge-Kutta).


Design and implementation

• The user API should be common for barrel and forward tracks.• However, the implementation is suggested to be separate and

complimentary for the barrel and the forward regions:• Optimal track search algorithms will differ for barrel and fwd.,

• Internal track representations may differ (e.g. 1/pT vs. 1/P),

• Coordinated independence of the two programming teams.

• A small MarlinReco control processor for the required top-level steering “barrel vs. fwd. calls”, transparent to the user.

• Coordination is enhanced by a common pool of utility classes; however, the skeleton GenFit is preferred over KalTest.

• Both implementations will rely on common interfaces, e.g. for• Using available results from a previous track search in TPC,

• Persistency by the new LCIO data model, augmented for GSF,

• Interfacing the new GEAR geometry toolkit (written by CERN).


Sharing of responsibilities

Discussions with F. Gaede and A. Ruiz at ILD Meetings in July & Oct. 2010, consent about sharing of tasks for the new ILD tracking:

• DESY Hamburg:Overall coordination and all barrel tracking: work has started.

• Spain (Santander, Valencia) and HEPHY Vienna:All forward tracking, with the sub-tasks

• (1,2) FTD geometry description, drivers in Mokka: Spain,• (3) FTD digitizations: Spain with contributions by Prague,• (4) FTD stand-alone fwd. track search: Spain and Vienna,• (5) TPC-supported fwd. track search: Vienna,• (6,7) DAF-based fits, precision track fit: Vienna.

Meanwhile, Paris VII (Aurore et al.) had contributed sub-tasks 1 and 2,

and will take care of sub-tasks 3 (with Prague) and 4 (with Vienna).


iLCsoft manpower @ Vienna


• Winni Mitaroff (head, will retire Dec. 2011, unpaid consultant thereafter)

• New undergraduate student:

– Robin Glattauer: Project work started 9 May on Marlin / MarlinReco, will be continued as a diploma thesis at TU Vienna July ‘11 – June ’12 on the new Forward Tracking (supervision by Winni M., backed by Rudi F.)

• Part-time support expected:

– Rudi Frühwirth (senior staff, statistics guru: Kalman, DAF, GSF …)

– Manfred Valentan (PhD student, mastermind fastsim tool “LiC Toy”)

– Wolfgang Waltenberger (junior staff, mastermind vertex tool RAVE)

• Aim at a first version of the new Forward Tracking to be used for the DBD !

• Possibly follow-on study on backgrounds in the forward region ?

Vienna’s contract with AIDA“Advanced European Infrastructures for Detectors at Accelerators”

• Official start at Kickoff Meeting,16-18 February 2011 at CERN• HEPHY participates in 2 of 9 “Working Packages” (contact: M. Krammer)

• WP 2: “Common Software Tools” (coordinators: F. Gaede, P. Mato)

• Task 2.2: “Geometry Toolkit for HEP”• Task 2.3: “Reconstruction Toolkits for HEP” (coord.: F. Gaede, DESY)

– Sub-task 2.3.a: “Tracking Toolkit” (coordinator: St. Aplin, DESY) * Sub2-task “Barrel Tracking”: DESY, ... * Sub2-task “Forward Tracking”: Santander, Valencia, Vienna

– Sub-task 2.3.b: “Alignment”– Sub-task 2.3.c: “Pile-up Events”– Sub-task 2.3.d: “PFA Calorimetry”

• Diploma student’s supervisor eligible for 1/3 salary refunding by AIDA

• Deliverable: generic toolkit within 38 months (due by end April 2014)


ILD vs. AIDA implementation

• AIDA sub-task 2.3.a– Deliverable: generic toolkit for Track Reconstruction.

– Timescale: February 2011 – April 2014 (38 months).

• ILD track reconstruction– Processor in MarlinReco: wrapped legacy Fortran code,

used for the 2009 LoI. Urgent need of new C++ code !

– Timescale: now – early 2012, to be used for the DBD.

• Pragmatic solution– Coding for ILD may serve as a “pilot implementation”.

– Needs clear separation generic vs. detector-dependent.

– Experience gained will be used for the AIDA deliverable.


Backup Slides


Software expertise at Vienna

• “Vienna School” of detector-related data analysis– Founded in the late 1970s by Meinhard Regler at HEPHY Vienna.

• Contributions to experiments since ~ mid 1980s– LEP-DELPHI, framework DELANA (f77): Local PR of FCA. Forward

track fit incl. VFT (Kalman), later merged with barrel for reprocessing.

– LHC-CMS, framework CMSSW (C++): Track and vertex reconstruction(Kalman, pioneering DAF, GSF). Offspring: vertex reco toolkit RAVE.

– Detector-independent tool LDT (MatLab) for fast simulation and trackreconstruction (Kalman). Used for optimizing ILD and CLIC detectors.

– KEKB-Belle II, framework BASF 2 (C++): Track search in SVD. Trackfit in PXD-SVD-CDC (Kalman, DAF, GSF). Both are still in progress.

• Dept. for Algorithms and Software Development– Headed by Rudi Frühwirth. A recent publication of general interest:

A. Strandlie and R. Frühwirth, Rev.Mod.Phys. 82 (2010) 1419-1458.


Mitaroff: Discussion document at ILD#5 and SiLC22 - 26 May 2011

Contributions to ILD by Vienna• ILD detector optimization:

– Evaluation of various tracker layouts, with emphasis on tracking quality in the difficult forward and intermediate regions.

– Development of optimization algorithms, and of a detector-independent fast simulation tool (“LiC Detector Toy” = LDT).

– Major contributions to the ILD “Letter of Intent”, which was the basis for IDAG’s 2009 approval of this detector concept.

• iLCsoft (Software for ILC Detectors):– Development of a detector-independent vertex reconstruction toolkit

(RAVE), based on “robust” algorithms developed for CMS.– Development of a new Track Reconstruction in the forward region of

the ILD detector (a major contribution, work starting now).

• SiLC (Silicon for Linear Colliders):– Generic R&D programme to develop low material budget high-precision

tracker modules, based on silicon micro-strip technology.– Design and construction of a Si envelope around a large prototype TPC

inside a superconducting magnet at a test beam at DESY.

14

What is the “forward region” ?• Very forward region

– 50 < ϑ < 11.50: only FTD measurements contributing,

– Range of FTD 1 (2) starts where that FTD 6 (7) ends.

• Intermediate region– 11.50 < ϑ < 25.50: complex mix of VTX + FTD + TPC,

– FTD: only FTD 1 … 3, plus FTD 4 until ϑ < 16.50,

– TPC: 10 pad-rows @ 11.50 … 100 pad-rows @ 25.50.

• Barrel + FTD 1 only– 25.50 < ϑ < 36.70: VTX + FTD 1 + SIT + TPC.

• ETD: 9.80 < ϑ < 36.90

– Ignored by track fitting: cannot contribute to precision,

– Useful for PFA (pattern recognition link to fwd. ECAL).


Forward tracking summary

• Forward track search:– Stand-alone in the FTD: careful choice among various algorithms,

– Combined TPC – FTD in the intermediate region (“time stamps”),

– Soft hit associations resolved later by the DAF.➯

• Forward track reconstruction:– Algorithms based on the Kalman Filter, with robustification by the

adaptive Deterministic Annealing Filter (DAF).

– (1) Testing and updating the track hypothesis (hit associations) by identifying and removing “outliers”, and resolving ambiguous associations from the track search,

– (2) Performing a precision track fit.

– Energy loss of electrons modeled by a Gaussian Sum Filter (GSF),

– Magnetic field distortions by the “anti-DiD” to be taken into account.

– Usage of a skeleton toolkit (GenFit or KalTest) ?


LDT example: forward optimization


(M. Valentan: presented at the 8th SiLC Meeting, Santander, Dec. 2008)

Track model for the GSF



Off topic: RAVE vertexing• Detector-independent vertex recon-struction toolkit: RAVE

– Developed 2004–08 by W. Waltenberger (master mind), F. Moser, B. Pflugfelder and H.V. Riedel,

– Interfaced to topological vertex search ZvTop,– Standard vertexing for CMS, Belle II (and 4th),– Pilot implementations in ILD’s “Marlin” and SiD’s Java-based “org.lcsim”

frameworks exist, but …

• The “rival”: LCFIvertex (tools ZvTop, ZvRes, ZvKin, ZvMst)– Developed by D.J. Jackson, S. Hillert, B. Jeffery et al., mostly at Oxford and RAL

until 2009; then support taken by Japan (Tohoku, KEK, Tokyo),– De-facto standard vertexing for ILD and SiD.

• New effort to reconcile RAVE with LCFIvertex:– Comparison study with ZvTop/ZvRes: recent meeting in Bonn 12 May 2011

(W. Waltenberger, S. Hillert et al.).

• W. Waltenberger: RAVE – a detector-independent toolkit to reconstruct vertices, IEEE Transactions on Nuclear Science, 2011, DOI 10.1109/TNS.2011.2119492 (08.03.2011).

Forward Tracking Report of the Vienna iLCsoft Group Winfried A. Mitaroff “Discussion document”...

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